[Katherine Swift]

This question comes from Jeff:

I am making an submergible light that will be used intermittently under water. I have considered using an epoxy or resin to encapsulate a SMD LED. I want the epoxy/resin to:
1. Waterproof the LED
2. Be clear enough for the light to transmit clearly through, and
3. Have a UV protector so it doesn’t turn yellow

My thought was to install the led chip, get the surface to be epoxy/resin level and pour a thin layer over the entire surface allowing it to work like self leveling cement. Is this possible? If so, what type of epoxy or resin would you recommend?

[Katherine Swift]

Hi Jeff,

I have not done this myself, but I have seen where others have done it with epoxy resin. Assuming the epoxy completely encloses everything that could be underwater (light, wiring, etc.), it would be waterproof. As long as you use a clear resin, it will be clear enough to see light transmitted through the resin. The challenge is going to be the yellowing part. Unfortunately, all resins are going to yellow over time. Resins with UV inhibitors and stabilizers help extend the time before yellowing occurs. However, things such as mixing off ratio (even though it still can cure without tackiness), putting over an improperly cured lacquer, excessive heat, and or constant exposure to sunlight can speed up the yellowing process. How long the epoxy will last in its clear state is very difficult to predict.

While using the resin as a coating could work, it is going to run off the sides and drip. (I haven’t used a self-leveling cement so I don’t know how that compares.) You will need to rotate the light several times during the first couple of hours to make sure the resin stays on and doesn’t completely leave the light.

Have you thought about casting the light with resin in a mold? I’m thinking using the resin and mold like you are making an outer casing may be easier. How big is your LED?

[Jeff gann]

The light will be in a cup style housing. Mounted to the bottom of the housing. The LED is 1″x1″ square and 2mm thick. Its very flat, yet very effective. (see SMD LED chip) As for a resin mold, I don’t think that will work since I need the interior to have a reflective surface for the exposure. The Leds have a run time of approx. 50,000 hours. If the resin turns yellow in that time frame, and I assume it would, Ill just have to see if it’ll still be doable.

[Katherine Swift]

Based upon your extra information, I would use the Resin Obsession crystal doming resin: https://shop.resinobsession.com/collections/resin/resin-obsession-crystal-doming-resin It mixes thick and is a doming resin. It will work to create a thin layer over the entire surface of your LED. Use the concepts I show here to make sure you don’t apply so much that it runs over the edge:

https://youtu.be/MrVj4JSpPzI

[Robert]

Will the resin be able to withstand the high heat the LED produces?

[Katherine Swift]

I don’t know. I can email the resin manufacturer and see what they can tell me.

[Anabel Lemus]

How long do I leave the uv light on for second, or minutes, so the resin mold can get hard.
Please let me know thank you!!!
Ms. Lemus

[Author]

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